Dear Professors
According to my literature survey, 0.25 kV/cm - 3 kV/cm is the field strength required for the electroporation to occur in mammalian cells. This field strength again depends on factors like cuvette gap size, cell diameter and temperature. What is ideal current that I can work with for this type of cells for a given cuvette gap size?
The field strength is equal to the voltage divided by the size of the gap between the electrodes, period. Temperature does not come into it, as the unit says (volts/cm). Hence a 1 kV/cm can be achieved with a 200 V pulse delivered in a 2-mm cuvette or a 400 V pulse delivered in a 4-mm cuvette.
Dear sir
I am also concerned with the current flowing to the electrodes because we are talking about 200 V (DC) and currents in the order of Amperes makes it very dangerous to work with as the power will be 200 Watts or above. Hence, is it possible to achieve the process in the current of the orders of mA with voltage of the order of few hundreds of volts (depending on the gap between the electrodes)?
The current does not electroporate cells, it is the field which is important.
Since, field is more important for the process to occur which depends on the voltage applied across the electrodes and the spacing between the two electrodes, I can work with the required voltage for a given cell and don't worry too much about the current that flows through the circuit.
Thank you madam for your insights. Julie Gehl
Exactly. However, the number of pulses and pulse duration should be kept within limits in order to keep the current low, and avoid heating. Examples of this is 8 pulses, of 0.1 ms. You can also work with low-conductivity buffers, as the group of Marie-Pierre Rols describes, if you want to have longer pulses.
Julie is completely correct and I think gave a pretty good explanation. Another way to think about electroporation in terms of the Maxwell stresses, as the electric field describes a force per unit charge. Then the field at and around the cell membrane is in some sense a sort of representation of the aggregate effects of the forces acting on the charged species within the vicinity of the cell membrane.
You're also right about the power--it is high (i.e. 200 W), but that just means you are you are pushing 200 J/s, and if the total energized time is, say 80 pulses at 0.1 ms/pulse (for irreversible electroporation), you are still less than 2 J, which is a lot lower energy than one might expect when hearing 1 A at 200 V.
Julie Gehl If the current is not important for the process, why are the electrodes in electroporation cuvettes in direct contact with the solution? Why not place them outside the tube, to limit the current flowing through the solution to virtually zero? Many thanks!
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